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sw_rast.js
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sw_rast.js
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(function(exports) {
"use strict";
var WIDTH = 400, HEIGHT = 400;
var CUBE = [
{ x: -1, y: -1, z: -1, attr: { u: 0, v: 0, } },
{ x: 1, y: -1, z: -1, attr: { u: 1, v: 0, } },
{ x: 1, y: 1, z: -1, attr: { u: 1, v: 1, } },
{ x: -1, y: 1, z: -1, attr: { u: 0, v: 1, } },
{ x: 1, y: -1, z: -1, attr: { u: 0, v: 0, } },
{ x: 1, y: -1, z: 1, attr: { u: 1, v: 0, } },
{ x: 1, y: 1, z: 1, attr: { u: 1, v: 1, } },
{ x: 1, y: 1, z: -1, attr: { u: 0, v: 1, } },
{ x: 1, y: -1, z: -1, attr: { u: 1, v: 0, } },
{ x: -1, y: -1, z: -1, attr: { u: 0, v: 0, } },
{ x: -1, y: -1, z: 1, attr: { u: 0, v: 1, } },
{ x: 1, y: -1, z: 1, attr: { u: 1, v: 1, } },
{ x: 1, y: -1, z: 1, attr: { u: 1, v: 0, } },
{ x: -1, y: -1, z: 1, attr: { u: 0, v: 0, } },
{ x: -1, y: 1, z: 1, attr: { u: 0, v: 1, } },
{ x: 1, y: 1, z: 1, attr: { u: 1, v: 1, } },
{ x: -1, y: -1, z: 1, attr: { u: 1, v: 0, } },
{ x: -1, y: -1, z: -1, attr: { u: 0, v: 0, } },
{ x: -1, y: 1, z: -1, attr: { u: 0, v: 1, } },
{ x: -1, y: 1, z: 1, attr: { u: 1, v: 1, } },
{ x: -1, y: 1, z: -1, attr: { u: 1, v: 0, } },
{ x: 1, y: 1, z: -1, attr: { u: 0, v: 0, } },
{ x: 1, y: 1, z: 1, attr: { u: 0, v: 1, } },
{ x: -1, y: 1, z: 1, attr: { u: 1, v: 1, } },
];
CUBE.forEach(function(p) {
p.attr.r = (p.x + 1) / 2.0 * 0xFF;
p.attr.g = (p.y + 1) / 2.0 * 0xFF;
p.attr.b = (p.z + 1) / 2.0 * 0xFF;
});
var CUBE_FACES = [
[0, 1, 2, 3],
[4, 5, 6, 7],
[8, 9, 10, 11],
[12, 13, 14, 15],
[16, 17, 18, 19],
[20, 21, 22, 23],
];
function edgeFunction(ax, ay, bx, by, px, py) {
// Put everything in the space of A.
bx -= ax; by -= ay; px -= ax; py -= ay;
// Signed area of the paralellogram decided by B and P.
return (bx * py - by * px);
}
function mixColor(ca, cb, t) {
var at = t, bt = 1-t;
var r = ((ca >>> 24) & 0xFF) * at + ((cb >>> 24) & 0xFF) * bt;
var g = ((ca >>> 16) & 0xFF) * at + ((cb >>> 16) & 0xFF) * bt;
var b = ((ca >>> 8) & 0xFF) * at + ((cb >>> 8) & 0xFF) * bt;
return r << 24 | g << 16 | b << 8;
}
function loadImage(src) {
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
var data = null;
ctx.load = function() {
if (!data)
data = ctx.getImageData(0, 0, ctx.canvas.width, ctx.canvas.height);
return data;
};
var img = document.createElement('img');
img.src = src;
img.onload = function() {
canvas.width = img.width;
canvas.height = img.height;
ctx.drawImage(img, 0, 0);
data = null;
};
return ctx;
}
var crate = loadImage('crate2.jpg');
function texture2D(img, u, v) {
var x = (img.width * u) | 0;
var y = (img.height * v) | 0;
var idx = (y * img.width + x) * 4;
return (img.data[idx + 0] << 24 | img.data[idx + 1] << 16 |
img.data[idx + 2] << 8 | img.data[idx + 3]);
}
function shadePixel(vtx) {
var texColor = texture2D(crate.load(), vtx.u, vtx.v);
var vtxColor = vtx.r << 24 | vtx.g << 16 | vtx.b << 8;
var color = mixColor(texColor, vtxColor, .5);
return color | 0x000000FF;
}
function renderTri(buffer, points, i1, i2, i3) {
// Our three points.
var P1 = points[i1];
var P2 = points[i2];
var P3 = points[i3];
// Edges.
var E1x1 = P2.x, E1y1 = P2.y, E1x2 = P3.x, E1y2 = P3.y;
var E2x1 = P3.x, E2y1 = P3.y, E2x2 = P1.x, E2y2 = P1.y;
var E3x1 = P1.x, E3y1 = P1.y, E3x2 = P2.x, E3y2 = P2.y;
// Extremeties.
var minX = (Math.min(P1.x, P2.x, P3.x) | 0);
var minY = (Math.min(P1.y, P2.y, P3.y) | 0);
var maxX = (Math.max(P1.x, P2.x, P3.x) | 0) + 1;
var maxY = (Math.max(P1.y, P2.y, P3.y) | 0) + 1;
// Clamp to image bounds.
minX = Math.max(minX, 0); minY = Math.max(minY, 0);
maxX = Math.min(maxX, WIDTH); maxY = Math.min(maxY, HEIGHT);
// Twice the tri's area.
var area = (P3.y - P1.y) * (P2.x - P1.x) - (P2.y - P1.y) * (P3.x - P1.x);
var img = buffer.img;
// Precompute inverses.
var P1_invW = 1/P1.w;
var P2_invW = 1/P2.w;
var P3_invW = 1/P3.w;
for (var y = minY; y < maxY; y++) {
for (var x = minX; x < maxX; x++) {
var E1 = edgeFunction(E1x1, E1y1, E1x2, E1y2, x, y);
var E2 = edgeFunction(E2x1, E2y1, E2x2, E2y2, x, y);
var E3 = edgeFunction(E3x1, E3y1, E3x2, E3y2, x, y);
// Inside our tri?
if (E1 < 0 || E2 < 0 || E3 < 0)
continue;
// Barycentric coordinates in clip space. Weights for
// how close we are to P1...
E1 /= area;
E2 /= area;
E3 /= area;
// Compute Z, which we can linearly interpolate in screen space...
var Z = P1.z*E1 + P2.z*E2 + P3.z*E3;
// Convert to 16-bit.
Z = Z * 0xFFFF;
// Early depth test.
var i = (y * img.width + x);
if (buffer.depth[i] < Z)
continue;
// Compute 1/P1.w*E1, etc.
var E1w = P1_invW*E1;
var E2w = P2_invW*E2;
var E3w = P3_invW*E3;
// Get our perspective-correct w.
var w = 1 / (E1w + E2w + E3w);
// Calculate vertex attributes.
var attr = {};
for (var k in P1.attr)
attr[k] = (P1.attr[k]*E1w + P2.attr[k]*E2w + P3.attr[k]*E3w) * w;
var p = shadePixel(attr);
var idx = i * 4;
img.data[idx + 0] = (p >>> 24) & 0xFF;
img.data[idx + 1] = (p >>> 16) & 0xFF;
img.data[idx + 2] = (p >>> 8) & 0xFF;
img.data[idx + 3] = p & 0xFF;
buffer.depth[i] = Z;
}
}
}
function renderFace(buffer, face, points) {
// Each face is guaranteed to be a quad.
if (face.length !== 4) XXX;
renderTri(buffer, points, face[0], face[1], face[2]);
renderTri(buffer, points, face[2], face[3], face[0]);
}
function memset(b, v) {
for (var i = 0; i < b.length; i++) b[i] = v;
}
function renderDepth(buffer, img) {
var o = 0;
for (var i = 0; i < buffer.length; i++) {
var v = (buffer[i] / 0xFFFF) * 0xFF;
img.data[o++] = v;
img.data[o++] = v;
img.data[o++] = v;
img.data[o++] = 255;
}
}
function renderModel(buffer, faces, points) {
// Clear.
memset(buffer.img.data, 0);
memset(buffer.depth, 0xFFFF);
faces.forEach(function(face) { renderFace(buffer, face, points); });
// renderDepth(buffer.depth, buffer.img)
buffer.ctx.putImageData(buffer.img, 0, 0);
}
function copy(o) {
var x = {};
for (var i in o)
x[i] = o[i];
return x;
}
function set(o, n) {
for (var k in n)
o[k] = n[k];
}
function rotateX(p, a) {
var sin = Math.sin(a),
cos = Math.cos(a);
var ry = p.y * cos - p.z * sin;
var rz = p.y * sin + p.z * cos;
return set(p, { y: ry, z: rz });
}
function rotateY(p, a) {
var sin = Math.sin(a),
cos = Math.cos(a);
var rx = p.x * cos + p.z * sin;
var rz = -p.x * sin + p.z * cos;
return set(p, { x: rx, z: rz });
}
function scalePoint(p, m) {
return set(p, { x: p.x * m, y: p.y * m, z: p.z * m });
}
function translatePoint(p, tx, ty, tz) {
return set(p, { x: p.x + tx, y: p.y + ty, z: p.z + tz });
}
function transform(points) {
return points.map(function(p) {
p = copy(p);
// Make it look cool by rotating it around...
rotateY(p, angle);
rotateX(p, angle * 0.7);
// So we're not in the immediate center of it.
translatePoint(p, 0, 0, +document.querySelector('#zoff').value);
// Perspective divide!
if (p.z <= 0)
p.z = 0.01;
p.w = p.z;
p.x /= p.w;
p.y /= p.w;
// The near plane is at 0, the far plane is at 10.
var FAR_PLANE = 10;
// Depth remap to [0-1].
var Z = p.z / FAR_PLANE;
// Clamp.
Z = Math.min(Math.max(Z, 0), 1);
scalePoint(p, +document.querySelector('#zoff').value);
// So we can see the point...
scalePoint(p, 80);
translatePoint(p, 200, 200, 200);
p.z = Z;
return p;
});
}
var angle = 0.25;
var buffer = {};
function init(ctx) {
buffer.img = ctx.getImageData(0, 0, ctx.canvas.width, ctx.canvas.height);
buffer.depth = new Uint16Array(buffer.img.width * buffer.img.height);
buffer.ctx = ctx;
}
function update(ctx) {
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
angle += 0.02;
var points = CUBE;
points = transform(points);
renderModel(buffer, CUBE_FACES, points);
}
window.onload = function() {
var canvas = document.createElement('canvas');
canvas.width = WIDTH;
canvas.height = HEIGHT;
document.body.appendChild(canvas);
var ctx = canvas.getContext('2d');
init(ctx);
function mainloop() {
update(ctx);
window.requestAnimationFrame(mainloop);
}
mainloop();
};
})(window);